The present invention is directed to an optical fiber ribbon having indicia thereon to enable the user to identify a particular fiber (e.g., fiber no. 1) and also to distinguish one optical fiber ribbon from another.
Optical fiber ribbons consist of a planar array of optical fibers joined together by a resin matrix material or the like. Such ribbons are becoming increasingly popular where optical fibers are used for data transmission and the like. This is due, in part, to the fact that optical fiber ribbons may contain a relatively large number of optical fibers in a package that allows for easy handling and installation. Further, because optical fiber ribbons reduce the need for manipulating individual optical fibers, optical fiber maintenance procedures are simplified. Often, a single cable will include numerous optical fiber ribbons, stacked one on another or otherwise disposed in the cable.
It is desirable to be able to easily identify and distinguish optical fiber ribbons one from another and to distinguish constituent elements of a given optical fiber ribbon, both before and after the ribbons are installed in the field for use. Conventionally, ribbon identification has been accomplished by printing characters, such as words, on the ribbon surface or using ink jet printing methods or by applying a bar code to the ribbon, as disclosed in U.S. Pat. No. 5,809,195. Once the identifying characters have been printed on the ribbon (using ink jet methods or the like), the printed characters are susceptible to smearing. Such smearing may render the printed characters illegible. Even when the characters are not smeared, their small size makes it very difficult to read them, particularly in the field where lighting conditions tend to be poor. Also, matching particular printed characters (e.g., particular languages) to particular markets and/or customers can be a difficult and expensive task.
It is also known in the art to color-code optical fibers for the purpose of positively identifying individual fibers. Conventionally, a thermosetting ink layer, a UV-cured ink or varnish layer, or the like, is coated on the fiber to give it a particular color (see, e.g., U.S. Pat. Nos. 5,446,821 and 5,377,292, the disclosures of which are incorporated herein by reference). Alternatively, pigments or dyes or any other coloring agents can be directly mixed into the material used to coat the fiber as it is drawn from an optical fiber preform. Such methods eliminate the additional step required to apply the ink or varnish layer. Moreover, it is known to combine the processes of fiber coloring with ribbon manufacturing.
More specifically, conventional optical fiber cables include optical fiber ribbons that are grouped together in sets (with each set having one or more, e.g., twelve, optical fibers) with each fiber in a particular set having a unique color. Thus, within a single ribbon, the optical fibers are coated with distinctly different colors. These distinct colors are repetitively used for each ribbon, so that if there are three ribbons, the optical fiber cable will have, e.g., three red optical fibers, three green optical fibers, etc. In order to distinguish between optical fibers having the same color, it is necessary to code each ribbon. This has been accomplished by applying varying numbers of marks (e.g., ink rings) to the ribbons, as disclosed in U.S. Pat. No. 5,379,363. None of the prior art addresses identifying fiber no. 1.
It is an object of the present invention to overcome the drawbacks of the prior art. More particularly, it is an object of the present invention to provide an optical fiber ribbon in which the location of a particular fiber contained in the ribbon can be easily identified in the field.
It is a further object of the present invention to use a common indicia for both identifying the particular fiber of each ribbon and to distinguish the ribbons from each other.
The present invention achieves the above and other objects and advantages by an optical fiber ribbon including a plurality of optical fibers, having outer coatings, arranged in parallel with and adjacent one another, and a ribbon matrix bonded to the outer coatings and encasing the plurality of optical fibers, wherein the ribbon matrix includes indicia on an outside thereof for directionally identifying a particular one of the optical fibers. According to a first aspect of the invention, the indicia includes triangle, with an apex of the triangle pointing in the direction of the particular fiber. Alternatively, according to a second aspect of the invention, the indicia includes an arrow, or any other geometrical shape that can be used to convey emphasis in a particular direction, pointing in the direction of the particular fiber. The indicia is preferably repeated at regular intervals along the length of the ribbon to allow the particular fiber to be identified along the entire length of the ribbon.
The invention is also directed to an optical fiber ribbon cable which includes a plurality of optical fiber ribbons. In this case, the indicia can also be used to distinguish between ribbons. For example, in the case where the indicia is a triangle, a first optical fiber ribbon can be identified by a single triangle repeated at regular intervals along the length of the ribbon and a second optical fiber ribbon can be identified by a pair of triangles repeated along the length of the ribbon. Alternatively, the ribbons can be identified with a different indicia for distinguishing between the ribbons. For example, the first ribbon can be identified by a single stripe extending between the triangles and the second ribbon can be identified by a pair of stripes extending between the pairs of triangles. Alternatively, the ribbon matrix material for each ribbon can have different colors as a way to distinguish one ribbon from another. Alternatively, the indicia used may itself be colored such that the color may vary from one ribbon to the next. For example, the first ribbon may be identified by a white triangle and the second ribbon may be identified by a blue triangle. It is also within the scope of the invention to include any possible combination of multiple embodiments within a cable, or grouping of ribbons, thus allowing for an increase in the number of ribbons, each with an independent indicia, possible.